A variety of mechanical tools are positioned and released hydraulically. These tools also provide for some type of mechanical release in the event of a hydraulic failure. Mechanical releases in generally cylindrical tools may employ a set of left hand threads that when engaged back the tool off of the device to which it was attached. In order to engage the left hand threads while the device remains stationary, the tool depends on friction acting on the device to create enough torque to allow the left hand threads to engage and back the tool out of the device.
Current oilfield technology provides a hydraulically operated tubing hanger running tool to lock and unlock a tubing hanger into a spool body force subsea wellhead. In emergency situations, when the running tool hydraulic system has failed such as by a blown seal or leak in the system and the tubing hanger running tool needs to be pulled. It is desirable to pull only the tubing hanger running tool and not the surrounding spool body and/or well casing and leaving the tubing hanger in place. A device that achieves this end would be highly desirable and less costly than current technology. Once the tubing hanger running tool has be retrieved, then a mechanical retrieval tool can be used to further pull the tubing hanger, if necessary.
Mechanically actuated releases for tubing hanger running tools rely on the friction and or shear weight of the tubing depending from the tubing hanger to supply sufficient torque to turn the tubing hanger running tool and actuate a set of left hand threads to back out the tool. However, there are several applications where the tubing is too light to create enough torque or the well is a directional well and the tubing bends and relieves the friction placed on the tubing hanger. In these situations, it is extremely difficult if not impossible to mechanically retrieve the running tool from the tubing hanger.
Another aspect of mechanically retrieving a tubing hanger and tubing hanger running tool is cost. It is very costly to retrofit an existing well completion system with a mechanical release because the casing string and/or spool body would need to be modified. The type of modification required, would necessarily have to be done when the spool body or casing is manufactured. It would be very beneficial to have a mechanical release system that can be installed in the tubing hanger without modifying the existing casing or spool body.